/* interface Pingable {
  ping(): void
}

class Sonar implements Pingable {
  ping() {
    console.log('ping!');
  }
}

class Ball implements Pingable {
  ping() {
    console.log('ping!');
  }
  pong() {

  }
} */

/* interface A {}
interface B {}

class C3 implements A ,B {

} */

/* interface Checkable {
  check(name: string) : boolean
}

class NameChecker implements Checkable {
  check(s: string) {
     return s.toLowerCase() === 'ok'
  }
} */


interface A {
  x: number
  y?: number
}

class C3 implements A {
  x = 0
  y = 1
}

const c = new C3()
console.log(c.x);
console.log(c.y);
